Actuator for controlling devices



Nov. 4, 1930. KOCH ET AL 1,780,302

ACTUATOR FOR CONTROLLING DEVICES Filed May 5, 1928 IWmini:4eviwwmwumm mmW I I i i 1 l LAWREA/(E fi [loci]: fiwm FDEVER- Patented Nov. 4, 1930UNITED STATES PAT ACTUATOR FOR CONTROLLING DEVICES Application filed May5, 1

This in vention relates to actuators for controlling devices such aselectrical switches and has special reference to a thermally opcratedactuator which is self compensating for room temperatures.

More particularly, this invention relates to a thermally operatedactuator as employed in electrical switches and other controlling meansand comprises a pair of bimetallic elements connected together andinsulated from each other, one of said elements being operated by anelectrical heater and the other of said elements being operated by theheat in a room or other enclosure. The aforesaid bimetallic elements arereversed or opposed with respect to each other; that is, a rise intemperature effects a warping of one of the members in the oppositedirection with respect to the other of the members.

Hereinafter, the present invention will be employed as a safety devicein an electrical circuit where it is desired to effect a circuit changeat a predetermined time, that is, to

control the period between the occurrence of a certain event and thetime when the switch shall have changed its circuit connections as inconnection with an automatic heating system. F or example, the actuatorfor this electrical switch is used in connection with what is commonlyknown as a stack switch, which latter controlsthe electrical heatingelement of the actuator. Upon failure of the heating system, the stackswitch, remaining in a cold position, will pass an electrical currentthrough the electrical heating element for an undue length of time toheat, and therefore, to warp the actuator into a position to tilt thecontactor, which action breaks the main line circuit.

One of the objects of this invention is to provide a thermally operatedactuator for operating the switching means of an electrical switch,which actuator is self compensating for room temperatures.

Another object of this invention is to provide a thermally operatedactuator which is simple in construction, durable, and inexpensive tomanufacture.

Other objects and advantages will hereinafter be more fully described,and for a 928. Serial No. 275,370.

more complete understanding of the characteristic features of thisinvention, reference may be had to the following description andaccompanying drawings, in which drawings: Figure l is a frontelevational view of an electrical switch employing the thermallyoperated actuator of this invention;

Fig. 2 is a front elevational view of the casing 10 with a cover 11pivotally secured thereto, a plurality of contact strips 12 secured toan insulated terminal block l3-and a second set of contact strips 14secured to a terminal block 15, both terminal blocks being secured toposts 1Q, which latter extend from the rear wall of the casing. I

A mercury tube contactor switch 17 is mounted in a clip 18, which latteris mounted on the upper side of a bimetallic element 19. The bimetallicmember 19 is, in turn, fixedly secured at one end thereof to one end ofa second bimetallic element 20, a preferably heat insulated joint beingformed therebetween by means of an insulating block 21 having securingmeans such as bolts and nuts 22 extending therethrough and through thebimetallic elements. The other end of the bimetallic element 20 issecured to an insulating block 23, which latter is, in turn, mounted inthe casing 10 and on the back wall thereof by means of suitable securingmembers.

The mercury tube contactor 17 is of the tiltable type comprising asealed container having a pair of spaced cooperating electrodes disposedat one end thereof and a body of current conducting fluid such asmercury also disposed therein, the fluid being adapted to bridge theelectrodes when tilted in one direction and to flow away from theelectrodes when tilted in the opposite direction. One Of the electrodesis suitably connected to one of the contact strips 12. The otherelectrode may,- if desired, be connected manner,

' into contact with and extend beyond the confines of the mem-' adjacenta heating element 24 in any suitable such as shown in Parks Patent No.1,644,443, and thence to one of the contact strips 14. The contactstrips 12 and 14 are thereafter connected in a circuit with variousother switches in an electrical system for controlling the operation ofthe fuel supplying means. It does not seem necessary to describe or showsuch a complete system in order to understand the operation of thisthermally operated actuator, and therefore, the same is omitted.

The heating element 24 preferably comprises a supporting member 25secured to the underneath side of the free end of the b1- metallicelement 19 in any suitable manner.

through The member 25 may be of any material, preferably of brass, andis provided with an insulatmg member on each side thereof, the lattermembers preferably being strips of mica around which a resistance wireis wound. The convolutions of the resistance wire are positively heldina spaced-apart relation as by means of coating the same with anasbestos composition which is thereafter permitted to harden. Theinsulating members prevent the resistance wire from coming thesupporting member 25 her 25 in order to receive binding posts 26, theends of the resistance wire being connected thereon. However, in lieu ofthe heating element just described, the resistance wire may be wounddirectly on the bimetallic element as shown particularly in the patentto Parks issued October 4, 1927, No. 1,644,443,

or the heating element may be of the form shown in a copendingapplication by Phelan,

filed December 22, 1926, and given Serial No. 156,343.

The bimetallic elements 19 and 20 are of the usual type comprising twometals having different coefiicients of expansion and which metals areintimately united at them and abutting surfaces for obtaining a movementof one part thereof relatively to the other part under temperaturechanges. One of the metals of each of the bimetallic elements will bereferred to as being of the higher order and the other metal will bereferred to as of the lower order. The metals of the same order of thetwo'bimetallic elements will occupy a reversed position in the that is,the metal of the 'In the operation of this switch, when the heatingelement 24 is supplied with current for an undue length of time the heatthus gentherethrough. The heat thus given off from the heating element24 is confined to the bimetallic member 19 and does not affect thebimetallic member 20, the latter being affected merely by the changes intemperature of the room or enclosure in which the device is located.Conversely, when the heating ele-' ment 24 is cooled, the bimetallicelement 19 assumes a normal condition to tilt the contactor 17 in anopposite direction to make an electrical circuit therethrough, thebimetallic member 20 not having any part in the operation excepting asthe temperature in the room may direct. I

In order to fully illustrate the relation of the bimetallic element 20with the actuation of the bimetallic element 19, it must be re-.membered that the temperatures of the enclosures in which the device isto be disposed may vary Widely. This variation in temperature oftheenclosure ordinarily would have an effect upon the bimetallic element19, for example, if the enclosure is comparatively cool, a greateramount of energy must be expended by the heating coil 24 to tilt thecontactor tube 17. Conversely, when the enclosure in which thedeviceflis positioned is comparatively warm, a less amount of energy isrequired by the heating element 24 to actuate the contactor 17. However,by means of V reversing the element 20 with respect to the element 19,in the manner aforesaid, the relative' positions of the elements 19 and20 remain unchanged because of the compensation effected as describedabove, therefore the same amount of energy from the heating element maybe expended to actuate a contactor in the instance of a comparativelywarm enclosure as would be required to actuate the contactor in theinstance of a comparatively cold enclosure.

While but a single embodiment of this invention is herein shown anddescribed, it is to be understood that various modifications may beapparent to those skilled in the art without departing from the spiritand scope of this invention, and therefore, the same is to be limitedonly by the scope of the prior art and the appended claims.

We claim:

1. In combination with a thermally operated actuator comprising aplurality of bimetallic elements connected together at their ends, oneof said bimetallic elements being electrically actuated and controlled,said bimetallic elements being opposed to each other whereby they areself compensating for room temperatures, of a mercury contactor switchme eee mounted Wholly on one of said bimetallic elements and adapted tobe tilted thereby.

2. In combination with a thermally operated actuator comprising abimetallic element fixed at one end thereof and controlled by thetemperature of the enclosure in which it is disposed, a secondbimetallic element connected to said first mentioned bimetallic element,said second bimetallic element bein electrically actuated, saidbimetallic elements being opposed to each other whereby they are selfcompensating for room temperatures, of a mercury contactor switchmounted wholly on the free end of said second bimetallic element andadapted to be tilted thereb 3 In combination with a thermal y operatedactuator comprising a straight bimetallic-element fixed at one endthereof, a second straight bimetallic element fixed to'the free end ofsaid first mentioned bimetallic element, said second bimetallic elementbeing electrically actuated,-said bimetallic elements being opposed toeach other whereby they are self compensating for room temperatures, ofa mercury contactor switch mounted wholly on the free end of said secondbimetallic element and adapted to be tilted thereby.

In witness whereof we have hereunto subscribed our names.

LAWRENCE E. KOCH. HENRY F. DEVER.

